High-mobility channel materials, which are capable of improving the carrier mobility of transistors, have been studied as a means of reducing power consumption and improving performance (operating characteristic) of a transistor. Improving the carrier transport property of a channel increases the drain current flowing when the channel is in ON-state, thereby allowing the power supply voltage to be decreased while obtaining a sufficient ON-state current. This combination brings about higher MOSFET performance at low electric power.
Group III-V compounds, such as gallium arsenide (GaAs), group IV materials, such as silicon germanium (SiGe) and germanium (Ge), and graphene, which consists of only carbon (C), have higher electron and hole mobility than that of silicon and an excellent carrier transport property, and are expected to be used as the high-mobility channel material. Particularly, a channel using a group IV material, which is easier in introduction than a group III-V compound, is positively studied. There is as yet no established technique for growing a group III-V compound channel with high crystallinity and controlling the channel to have a desired shape. Also, the group III-V compound channel has no advantage in terms of cost over the channel using a group IV material.
A high-mobility material channel can be formed by polishing an object including a high-mobility material portion and a silicon material portion. In this case, when a polishing composition is used that can polish the high-mobility material portion with higher selectivity over the silicon material portion, the high-mobility material portion can be efficiently polished and removed. Also, since loss of oxide such as silicon oxide is decreased, a withstand voltage between wiring layers is secured. Further, in a subsequent photolithography process, the decreased loss of oxide facilitates focusing of the exposure light, thereby stabilizing the process (see Patent Document 1). However, a polishing composition described in, for example, Patent Document 2 or 3 and conventionally used for polishing a compound semiconductor substrate consisting of only a group IV compound does not, when used for polishing an object including a high-mobility material portion and a silicon material portion, exhibit sufficiently high polishing selectivity for the high-mobility material portion.